21 July 2026

Three-point hitch parts – a guide to categories and measurements

The three-point hitch is a fundamental part of a tractor's design and determines how implements are attached to the machine. There are several different components to keep track of, as well as various categories with specific measurements. Product range developer Stefan Ekblad, Olsson Parts, answers and explains.

What do the different categories of three-point hitch parts mean?
When talking about three-point hitch parts for tractors – such as top links and lower link arms – they are divided into categories depending on their size. This classification is determined by the dimensions of the pins that hold the parts together, and it determines the size of tractor and implement the parts are suitable for.

Generally speaking:
Category 1 – most common on garden tractors, older models and smaller tractors.
Category 2 – standard on small to medium-sized tractors, up to around 100 horsepower.
Category 3 – follows on from Category 2, for larger tractors and machinery.
Category 4 – the very largest tractors and heaviest implements.

Why the odd decimal figures?
The fact that the measurements are often given as decimals such as 19.1 mm, 25.4 mm or 38.1 mm is because they were originally inch-based measurements converted to millimetres.
– That's why you see measurements such as 25.4 and 50.8; they are old inch-based measurements, says Stefan.

Hooks, quick couplers and balls
An important detail is the balls in the quick couplers, particularly when using hooks. It is not just the pin's diameter that matters here, but also the external size of the ball – this varies between 50.8 mm for category 2 and 78 mm for category 4.
– On some tractors, categories are also mixed, for example a category 2 hole with a category 3 ball. This is a deliberate simplification – rather than having a precisely matching part for each category, a combination is used that covers more tractors and implements, thereby reducing the number of variants needed in the assortment, explains Stefan.

Bushings and combination solutions
Bushings are often used to adapt implements to different tractors. This makes it possible, for example, to connect a category 2 implement to a category 3 lower link arm. There are also clever solutions featuring balls with double holes, allowing you to switch between different categories.
– You simply turn the ball, and suddenly you have both category 1 and 2 available.

Spare parts and repairs
For those with worn parts, the market offers both complete lower link arms and repair ends, which include welded ends for hook or ball attachments. There are also complete repair kits for various makes such as CBM, Walterscheid and LH Lift.
– If you don't want to replace the whole lower link arm, you can simply weld on a new end, explains Stefan.

The right measurements ensure the right coupling
In summary, it is important to measure correctly, to know the relevant measurements for each category, and to combine the parts in the right way. Sometimes it's not enough just to check the pin's diameter – the size of the ball and any mix of categories must also be correct for the coupling to be secure and function as intended.
– With the right bushings, balls and quick couplers, it's also possible to adapt even older equipment to today's implements and requirements. And you can do so without having to replace the whole three-point hitch, notes Stefan.

Watch the video on Olsson Parts' YouTube channel. Tinkering tips with Olsson Parts – Three-point hitch parts

Important to bear in mind:
Check which category (1–4) applies to your tractor – this determines which three-point hitch parts are compatible.
Top links and lower link arms have different pin diameters within the same category – do not mix up the measurements.
With quick couplers and hooks, it's not enough to check the pin diameter – the external size of the ball also matters.
Categories can be mixed (e.g. a category 2 hole with a category 3 ball) – always check both measurements, not just one.
Bushings and balls with double holes can be used to adapt implements between different categories.
In the event of wear and tear, it is not always necessary to replace the whole lower link arm – repair ends and repair kits are available for several makes.

The measurements differ between top links and lower link arms:
Category
Top link diameter
Lower link arm diameter

Three-point hitch parts are crucial for the safe attachment of implements to the tractor. Stefan Ekblad, Olsson Parts, explains the different categories and measurements, as well as the importance of checking pin diameters and balls.
The correct measurements for pins and balls are absolutely essential. Stefan Ekblad, Olsson Parts, explains the components and measurements of the three-point hitch.